University of Virginia Library

Chapter 16
The Law of Evolution continued

§128. But does this generalization express the whole truth? Does it include everything essentially characterizing Evolution and exclude everything else? Does it comprehend all the phenomena of secondary redistribution which Compound Evolution presents, without comprehending any other phenomena? A critical examination of the facts will show that it does neither.

Changes from the less heterogeneous to the more heterogeneous, which are not included in what we here call Evolution, occur in every local disease. In a morbid growth we see a new differentiation. Whether this morbid growth be, or be not, more heterogeneous than the tissues in which it is seated, is not the question. The question is whether the organism as a whole is, or is not, rendered more heterogeneous by the addition of a part unlike every pre-existing part, in form, or composition, or both. To this question there can be none but an affirmative answer. Again, the earlier stages of decomposition in a dead body involve increase of heterogeneity. Supposing the chemical changes to commence in some parts sooner than in others, as they commonly do, and to affect different tissues in different ways, as they must, it seems clear that the entire body, made up of undecomposed parts and parts decomposed in various modes and degrees, has become more heterogeneous than it was. Though grater homogeneity will be the eventual result, the immediate result is certainly not Evolution. Other instances are furnished by social disorders and disasters. A rebellion which, while leaving some provinces undisturbed, develops itself here in secret societies, there in public demonstrations, and elsewhere in actual conflicts, necessarily renders the society, as a whole, more heterogeneous. Or when a dearth causes commercial derangement with its entailed bankruptcies, closed factories, discharged operatives, food-riots, incendiarisms; it is manifest that as a large part of the community retains its ordinary organization displaying the usual phenomena, these new phenomena must be regarded as adding to the complexity previously existing. But such changes, so far from constituting further Evolution, are steps towards Dissolution.

So that the definition arrived at in the last chapter is an imperfect one. The changes above instanced as coming within the formula as it now stands, are so obviously unlike the rest, that the inclusion of them implies some distinction hitherto overlooked. Such further distinction we have now to supply.

§129. At the same time that Evolution is a change from the homogeneous to the heterogeneous, it is a change from the indefinite to the definite. Along with an advance from simplicity to complexity, there is an advance from con fusion to order — from undetermined arrangement to determined arrangement. Development, no matter of what kind, exhibits not only a multiplication of unlike parts, but an increase in the clearness with which these parts are marked off from one another. And this is the distinction sought. For proof, it needs only to reconsider the instances given above. The changes constituting local disease, have no such definiteness, either in place, extent, or outline, as the changes constituting development. Though certain morbid growths are more common in some parts of the body than in others (as warts on the hands, cancer in the breasts, tubercle in the lungs), yet they are not confined to these parts; nor, where found, are they anything like so precise in their relative positions as are the normal parts around. Their sizes are very variable: they bear no such constant proportions to the body as organs do. Their forms, too, are far less specific than organic forms. And they are extremely confused in their internal structures. That is, they are in all respects comparatively indefinite. The like peculiarity may be traced in decomposition. That total indefiniteness to which a dead body is finally reduced, is a state towards which the putrefactive changes tend from their commencement. The advancing destruction of the organic compounds blurs the tissue-structures — diminishes their distinctness. From the portions that have undergone most decay, there is a gradual transition to the less decayed portions, not a sharp demarcation. And step by step the lines of organization, once so precise, disappear. Similarly with social changes of an abnormal kind. The disaffection initiating a political outbreak, implies a loosening of those ties by which citizens are bound up into distinct classes and sub-classes. Agitation, growing into revolutionary meetings, fuses ranks that are usually separated. Acts of insubordination break through the ordained limits to individual conduct, and tend to obliterate the lines between those in authority and those beneath them. At the same time arrest of trade causes artizans and others to lose their occupations; and, ceasing to be functionally distinguished, they merge into an indefinite mass. When at last there comes positive insurrection, all magisterial and official powers, all class distinctions, all industrial differences, cease: organized society lapses into an unorganized aggregate of social units. Similarly, in so far as famines and pestilences cause changes from order towards disorder, they cause changes from definite arrangements to indefinite arrangements.

Thus, then, is that increase of heterogeneity which is not a trait of Evolution, distinguished from that increase of heterogeneity which is. Though in disease and after death, individual or social, the earliest modifications are additions to the pre-existing heterogeneity, they. are not additions to the pre-existing definiteness. From the outset they begin to destroy this definiteness, and gradually produce a heterogeneity that is indeterminate instead of determinate. As a city, already multiform in its variously-arranged structures of various architecture, may be made more multiform by an earthquake, which leaves part of it standing and overthrows other parts in different ways and degrees, but is at the same time reduced from orderly arrangement to disorderly arrangement; so may organized bodies be made for a time more multiform by changes which are nevertheless disorganizing changes. And in the one case as in the other, it is the absence of definiteness which distinguishes the multiformity of regression from the multiformity of progression.

If advance from the indefinite to the definite is an essential characteristic of Evolution, we shall of course find it everywhere displayed; as in the last chapter we found displayed the advance from the homogeneous to the heterogeneous. To see whether it is so, let us now consider the same several classes of facts.

§130. Beginning, as before, with a hypothetical illustration, we have to note that each step in the evolution of the Solar System, supposing it to have originated from diffused matter, was an advance towards more definite structure. As usually conceived, the initial nebula was irregular in shape and with indistinct margins, like those of nebulae now existing. Having partially-different proper motions, the parts of its attenuated substance, while being drawn together, generated, by the averaging of their motions, as well as by changes in the directions of these motions, a certain angular momentum; and the entire mass as it concentrated and acquired rotation must have assumed the form of an oblate spheroid which with every increase of density, became more specific in outline, and had its surface more distinctly marked off from the surrounding void. Simultaneously, the constituent portions of nebulous matter, instead of moving round their common centre of gravity in various planes, as they would at first do, must have had these planes more and more merged into a single plane, that became less vague as the concentration progressed — became gradually defined.

According to the hypothesis, change from indistinct characters to distinct ones, was repeated in the evolution of planets and satellites. A gaseous spheroid is less definitely limited than a liquid spheroid, since it is subject to larger undulations of surface, and to greater distortions of general form; and, similarly, a liquid spheroid, covered as it must be with waves of various magnitudes, tidal and other, is less definite than a solid spheroid. The decrease of oblateness which goes along with increase of integration, brings relative definiteness of other elements. A concentrating planet having an axis inclined to the plane of its orbit, must, while very oblate, have its plane of rotation much disturbed by external attractions; whereas its approach to a spherical form, involves a smaller precessional motion, and less marked variations in the direction of its axis.

With progressing settlement of the space-relations, the force-relations simultaneously become more settled; and the exact calculations of physical astronomy show us how definite these force-relations now are. In short, it needs but to think of the contrast between the chaos of the primitive nebula and the ordered relations of the Solar System in the sizes, shapes, motions, and combined inter-actions of its members, to see that increase of definiteness has been a marked trait of its evolution.

§131. From that primitive molten state of the Earth inferable from geological data as well as from the nebular hypothesis (probably a liquid shell having a nucleus of gases above the "critical point" of temperature, kept by pressure at a density as great as that of the superjacent liquid) the transition to its existing state has been through stages in which the characters became more determinate. A liquid spheroid is less specific than a solid spheroid in having no fixed distribution of parts. Currents of molten matter, though kept to certain general circuits by the conditions of equilibrium, cannot, in the absence of solid boundaries, be precise in their limits and directions: all parts must be in motion with respect to other parts. But a superficial solidification, even though partial, is a step towards the establishment of definite relations of position. In a thin crust, however, often ruptured by disturbing forces, and moved by every tidal undulation, fixity of relative position can be but temporary. Only as the crust thickens can there arise distinct and settled geographical positions. Observe, too, that when, on a surface adequately cooled, there begins to precipitate the water floating above as vapour, the deposits cannot maintain definiteness either of state or place. Falling on a solid envelope not thick enough to preserve anything beyond slight variations of level, the water must form small and shallow pools over the coolest areas; which areas must pass insensibly into others that are too hot to allow condensation. With progressing refrigeration, however — with a thickening crust, a consequent formation of larger elevations and depressions, and the precipitation of more atmospheric water, there comes an arrangement of parts which is comparatively fixed; and the definiteness of position increases, until there result continents and oceans — a distribution that is not only topographically settled, but presents separations of land from water more definite than could have existed when all the uncovered areas were low islands with shelving beaches, over which the tide ebbed and flowed to great distances.

Respecting the characters classed as geological, we may draw kindred inferences. While the Earth's crust was thin, mountain-chains were impossibilities: there could not have been long and well-defined axes of elevation, with distinct water-sheds and areas of drainage. Moreover, the denudation of small islands by small rivers, and by tidal streams both feeble and narrow, would produce no clearly-marked sedimentary strata. Confused and varying masses of detritus, such as we now find at the mouths of brooks, must have been the prevailing formations. And these could give place to distinct strata, only as there arose continents and oceans, with their great rivers, long coast-lines, and wide-spreading marine currents.

There must simultaneously have resulted more definite meteorological conditions. Differences of climates and seasons grew relatively decided as the heat derived from the Sun became distinguishable from the proper heat of the Earth; and the production of more specific conditions in each locality was aided by increasing permanence in the distribution of lands and seas. These are conclusions sufficiently obvious.

§132. We come now to the evidence yielded by organic bodies. In place of deductive illustrations, we shall here find illustrations which have been inductively established, and are therefore less open to criticism. The course of mammalian development, for example, will supply us with numerous proofs ready-described by embryologists.

The first change which the ovum of a mammal undergoes after repeated segmentation has reduced it to a mulberry-like mass, is the appearance of a distinction between the peripheral or epiblastic cells of this mass and the internal or hypoblastic cells. While growing rapidly the cluster of cells becomes hollow, and the blastodermic vesicle so formed presents a definite contrast between the outer layer, or epiblast, and its contents. The mass of hypoblast cells, having at first an indefinite, lens-like figure attached to the inside of the epiblast, spreads out and flattens into a membrane, the boundary of which is irregular — indefinite alike in form and constitution. And then the middle or thicker part presently becomes an opaque circular spot constituting the embryonic area: a spot which gradually acquires a pronounced outline. In the centre of this there at length comes the primitive streak or trace, which, as its name implies, is indefinite but by-and-by "becomes a more pronounced structure." Within this streak or trace the vertebrate axis first shows itself. Beginning as a shallow groove, it becomes slowly more pronounced; its sides grow higher; their summits overlap and at last unite; and so the indefinite groove passes into a definite tube, forming the vertebral canal. In this vertebral canal the leading divisions of the brain are at first discernible only as slight bulgings; while the proto-vertebrae commence as indistinct modifications of the tissue bounding the canal. Meanwhile in kindred ways the indefinite out-spread membrane through which are absorbed the materials for the unfolding structures around, is changed, into a definite alimentary canal. And in an analogous manner the entire embryo, which at first lies outspread on the yelk-sack, gradually rises up from it, and by the infolding of its ventral region becomes a separate mass, definitely outlined, connected with the yelk-sack only by a narrow duct.

These changes through which the general structure is marked out with slowly-increasing precision, are paralleled in the evolution of each organ. The liver commences by multiplication of certain cells in the wall of the intestine. The thickening produced by this multiplication, "increases so as to form a projection upon the exterior of the canal — a hollow bud;" and at the same time that the organ grows and becomes distinct from the intestine, the channels running through it are transformed into ducts having clearly-marked walls. Similarly, certain cells of the external coat of the alimentary canal at its upper portion, accumulate into lumps or buds from which the lungs are developed; and these, in their general outlines and detailed structure, acquire distinctness step by step. But even were no examples given, it would be undeniable that since a simple cluster of similar cells grows into head, trunk, and limbs of distinct shapes, each made up of many organs containing parts severally having clear outlines and composed of specific tissues, increase of definiteness has been a leading trait of the transformation.

Changes of this order continue long after birth; and, in the human being, are some of them not completed till middle life. During youth, most of the articular surfaces of the bones remain rough and fissured — the calcareous deposit ending irregularly in the surrounding cartilage. But between puberty and the age of thirty, these articular surfaces are finished off into smooth, hard, sharply-cut "epiphyses." Generally, indeed, we may say that increase of definiteness continues when there has ceased to be any appreciable increase of heterogeneity. And there is reason to think that those modifications which take place after maturity bringing about old age and death, are modifications of this nature; since they cause rigidity of structure, a consequent restriction of movement and of functional pliability, a gradual narrowing of the limits within which the vital processes go on, ending in an organic adjustment too precise — too narrow in its margin of possible variation to permit the requisite adaptation to changes of external conditions.

§133. To give clear proof that the Earth's Flora and Fauna, regarded either as wholes or in their separate species, have progressed in definiteness, is no more possible than it was to prove that they have progressed in heterogeneity: the facts are not sufficient. If, however, we allow ourselves to reason from the hypothesis, now daily rendered more probable, that every species has arisen through the accumulation of modifications upon modifications, just as every individual arises. we shall see that there must have been a progress, from the indeterminate to the determinate, both in the particular forms and in the groups of forms.

We may set out with the significant fact that the lowest organisms (which are analogous in structure to the germs of all higher ones) have so little definiteness that it is difficult, if not impossible, to decide whether they are plants or animals. Respecting sundry of them there are unsettled disputes between zoologists and botanists. Note next that among the Protozoa, great indefiniteness of shape is general. Of sundry shell-less Rhizopods the form is so irregular as to admit of no description: it is neither alike in any two individuals nor in the same individual at successive moments. By aggregation of Protozoa, are produced, among other creatures, the Sponges, most of which are indefinite in size, in contour, in internal arrangement; and such more definite aggregates as the Hydra are made indefinite both by the great differences between their contracted and expanded states and by their reproductive developments. As further showing how relatively indeterminate are the simplest organisms, it may be mentioned that their structures vary greatly with surrounding conditions: so much so that, among the Protozoa and Protophyta, many forms which were once classed as distinct species, and even as distinct genera, are found to be merely varieties of one species. If, now, we call to mind how precise in their traits are the highest organisms — how sharply cut their outlines, how invariable their proportions, and how comparatively constant their structures under changed conditions; we cannot deny that greater definiteness is one of their characteristics. If they have been evolved out of lower organisms, increase of definiteness has been an accompaniment of their evolution.

That, in course of time, species have become more sharply marked off from other species, genera from genera, and orders from orders, is a conclusion not admitting of a more positive establishment than the foregoing. If, however, species and genera and orders have arisen by evolution, then, as Mr. Darwin shows, the contrasts between groups must have become greater. Disappearance of intermediate forms, less fitted for special spheres of existence than the extreme forms they connected, must have made the differences between the extreme forms decided; and so, from indistinct varieties, must have been produced distinct species: an inference which is in harmony with what we know respecting races of men and races of domestic animals.

§134. The successive phases through which societies pass, obviously display the progress from indeterminate arrangements to determinate arrangements. A wandering tribe of savages, being fixed neither in its locality nor in its internal distribution, is far less definite in the relative positions of its parts than a nation. In such a tribe the social relations are confused and unsettled. Political authority is vague. Distinctions of rank are neither clearly marked nor impassable. And save in the different occupations of men and women, there are no decided industrial divisions. Only in tribes of considerable size, which have enslaved other tribes, is economic differentiation distinct.

But one of these primitive societies that evolves, becomes step by step more specific. Increasing in size, consequently ceasing to be so nomadic, and restricted in its range by neighbouring societies, it acquires, after prolonged border warfare, a settled territorial boundary. The distinction between the ruling race and the people, sometimes amounts, in the popular belief, to a difference of nature. The warrior-class attains a perfect separation from classes devoted to the cultivation of the soil or to other occupations regarded as servile. And there arises a priesthood which is defined in its rank, its functions, its privileges. This sharpness of definition, growing both greater and more variously exemplified as societies advance to maturity, is extremest in those which have reached their full development or are declining. Of ancient Egypt we read that its social divisions were precise and its customs rigid. Recent investigations make it more than ever clear that among the Assyrians and surrounding peoples, not only were the laws unalterable, but even the minor habits, down to those of domestic routine, Assessed a sacredness which insured their permanence. In India at the present day, the unchangeable distinctions of caste, not less than the constancy in modes of dress, industrial processes, and religious observances, show how definite are the arrangements where the antiquity is great. Nor does China, with its long-settled political organization, its elaborate and precise conventions, fail to exemplify the same truth.

The successive phases of our own and adjacent societies, furnish facts somewhat different in kind but similar in meaning. Originally monarchical authority was more baronial, and baronial authority more monarchical, than afterwards. Between modern priests and the priests of old times, who while officially teachers of religion were also warriors, judges, architects, there is a marked difference in definiteness of function. And among the people engaged in productive occupations, like contrasts hold: the regulative parts have become definitely distinct from the operative parts and the distributive parts from both. The history of our constitution, reminding us how the powers of King, Lords, and Commons have been gradually settled, describes analogous changes. Countless facts bearing the like construction meet us when we trace the development of legislation; in the successive stages of which we find statutes gradually rendered more specific in their applications to particular cases. Even now each new law beginning as a vague proposition, is, in the course of enactment, elaborated into specific clauses; and only after its interpretation has been established by judges' decisions in courts of justice, does it reach its final definiteness. From the annals of minor institutions like evidence may be gathered. Religious, charitable, literary, and all other societies, starting with ends and methods roughly sketched out and easily modifiable, show us how, by the accumulation of rules and precedents, the purposes become more precisely formulated and the modes of action more restricted; until at last decay follows a fixity which admits of no adaptation to new conditions. Should it be objected that among civilized nations there are examples of decreasing definiteness (instance the breaking down of limits between ranks), the reply is, that such apparent exceptions are the accompaniments of a social metamorphosis — a change from the military type of social structure to the industrial type, during which old lines of structure are disappearing and new ones becoming more marked.

§135. All organized results of social action — all super-organic structures, pass through parallel phases. Being, as they are, objective products of subjective processes, they must display corresponding changes; and that they do this, the cases of Language, of Science, of Art, clearly prove.

Strike out from our sentences everything but nouns and verbs, and there stands displayed the vagueness characterizing undeveloped tongues. Each inflection of a verb, or addition by which the case of a noun is marked, by limiting the conditions of action or of existence, enables men to express their thoughts more precisely. That the application of an adjective to a noun, or an adverb to a verb narrows the class of things or changes indicated, implies that the additional word serves to make the proposition more distinct. And similarly with other parts of speech.

The like effect results from the multiplication of words of each order. When the names for objects, and acts, and qualities, are but few, the range of each is proportionately wide, and its meaning therefore unspecific. The similes and metaphors so much used by aboriginal races, indirectly and imperfectly suggest ideas which they cannot express directly and perfectly from lack of words. Or to take a case from ordinary life, if we compare the speech of the peasant who, out of his limited vocabulary, can describe the contents of the bottle he carries, only as "doctor's stuff" which he has got for his "sick" wife, with the speech of the physician, who tells those educated like himself the particular composition of the medicine and the particular disorder for which he has prescribed it; we have vividly brought home to us the precision which language gains by the multiplication of terms.

Again, in the course of its evolution, each tongue acquires a further accuracy through processes which fix the meaning of each word. Intellectual intercourse slowly diminishes laxity of expression. By-and-by dictionaries give definitions. And eventually, among the most cultivated, indefiniteness is not tolerated, either in the terms used or in their grammatical combinations.

Once more, languages considered as wholes become more sharply marked off from one another, and from their common parent; as witness, in early times, the clear distinction that arose between the two connate languages Greek and Latin, and in later times the divergence of three Latin dialects into Italian, French, and Spanish.

§136. In his History of the Inductive Sciences, Dr. Whewell says that the Greeks failed in physical philosophy because their "ideas were not distinct, and appropriate to the facts." I do not quote this remark for its luminousness; since it would be equally proper to ascribe the indistinctness and inappropriateness of their ideas to the imperfection of their physical philosophy; but I quote it because it serves as good evidence of the indefiniteness of primitive science. The same work and its fellow, The Philosophy of the Inductive Sciences, yield other evidences equally good, because equally independent of any such hypothesis as is here to be established. Respecting mathematics, we have the fact that geometrical theorems grew out of empirical methods; and that these theorems, at first isolated, did not acquire the clearness which demonstration gives, until they were arranged by Euclid into a series of dependent propositions. At a later period, the same general truth was exemplified in the progress from the "method of exhaustions" and the "method of indivisibles" to the "method of limits;" which is the central idea of the infinitesimal calculus. in early mechanics may be traced a dim perception that action and reaction are equal and opposite; though, for ages after, this truth remained unformulated. And similarly, the property of inertia, though not distinctly comprehended until Kepler lived, was vaguely recognized long before. "The conception of statical force," "was never presented in a distinct form till the works of Archimedes appeared;" and "the conception of accelerating force was confused, in the mind of Kepler and his contemporaries, and did not become clear enough for purposes of sound scientific reasoning before the succeeding century." To which specific assertions may be added the general remark, that "terms which originally, and before the laws of motion were fully known, were used in a very vague and fluctuating sense, were afterwards limited and rendered precise." When we turn from abstract scientific conceptions to the concrete previsions of science, of which astronomy furnishes numerous examples, a like contrast is visible. The times at which celestial phenomena will occur, have been predicted with ever-increasing accuracy. Errors once amounting to days are now diminished to seconds. The correspondence between the real and supposed forms of orbits has been gradually rendered more precise. Originally thought circular, then epicyclical, then elliptical, orbits are now ascertained to be curves which always deviate from perfect ellipses, and are ever undergoing changes.

But the general advance of Science in definiteness is best shown by the contrast between its qualitative stage and its quantitative stage. At first the facts ascertained were that between such and such phenomena some connexion existed — that the appearances a and b always occurred together or in succession; but it was known neither what was the nature of the relation between a and b, nor how much of a accompanied so much of b. The development of Science has in part been the reduction of these vague connexions to distinct ones. Most relations have been classed as mechanical, chemical, thermal, electric, magnetic, etc.; and we have learnt to infer the relative amounts of the antecedents and consequents with exactness. Of illustrations, some furnished by physics have been given, and from other sciences plenty may be added. We have ascertained the constituents of numerous compounds which our ancestors could not analyze, and of a far greater number which they never even saw; and the combining equivalents of the elements are now accurately calculated. Physiology shows advance from qualitative to quantitative prevision in ascertaining definite relations between organic products and the materials consumed; as well as in measurement of functions by spirometer and sphygmograph. By Pathology it is displayed in the use of the statistical method of determining the sources of diseases, and the effects of treatment. In Botany and Zoology, the numerical comparisons of Floras and Faunas, leading to specific conclusions respecting their sources and distributions, illustrate it. And in Sociology, questionable as are many conclusions drawn from the classified sum-totals of the census, from the Board-of-Trade tables, and from criminal returns, it must be admitted that these imply a progress towards more precise conceptions of social phenomena.

That an essential characteristic of advancing Science is increase in definiteness, appears indeed almost a truism, when we remember that Science may be described as definite knowledge, in contradistinction to that indefinite knowledge possessed by the uncultured. And if, as we cannot question, Science has, in the course of ages, been evolved out of this indefinite knowledge of the uncultured, then, the gradual acquirement of that great definiteness which now distinguishes it, must have been a leading trait in its evolution.

§137. The arts, industrial and aesthetic, supply illustrations perhaps still more striking. Palaeolithic flint implements show the extreme want of precision in men's first handiworks. Though a great advance on these is seen in the tools and weapons of existing savage tribes, yet an inexactness in forms and fittings distinguishes such tools and weapons from those of civilized races. In a smaller degree, the productions of the less-advanced nations are characterized by like defects. A Chinese junk, with all its contained furniture and appliances, nowhere presents a line that is quite straight, a uniform curve, or a true surface. Nor do the utensils and machines of our ancestors fail to exhibit a similar inferiority to our own. An antique chair, an old fireplace, a lock of the last century, or almost any article of household use that has been preserved for a few generations, proves by contrast how greatly the industrial products of our time excel those of the Past in their accuracy. Since planing machines have been invented, it has become possible to produce absolutely straight lines, and surfaces so truly level as to be air-tight when applied to each other. While in the dividing-engine of Troughton, in the micrometer of Whitworth, in microscopes that show fifty thousand divisions to the inch, and in ruled divisions up to 200,000, we have an exactness as far exceeding that reached in the works of our great-grandfathers, as theirs exceeded that of the aboriginal celt-makers.

In the Fine Arts there has been a parallel progress. From the rudely-carved and painted idols of savages, through the early sculptures characterized by limbs without muscular detail, wooden-looking drapery, and faces devoid of individuality, up to the later statues of the Greeks or some of those now produced, the increased accuracy of representation is conspicuous. Compare the mural paintings of the Egyptians with the paintings of medieval Europe, or these with modern paintings, and the more precise rendering of the appearances of objects is manifest. It is the same with fiction and the drama. In the marvellous tales current among Eastern nations, in the romantic legends of feudal Europe, as well as in the mystery-plays and those immediately succeeding them, we see great want of correspondence to the realities of life; alike in the predominance of supernatural events, in the extremely improbable occurrences, and in the vaguely-indicated personages. Along with social advance, there has been a progressive diminution of unnaturalness — an approach to truth of representation. And now, cultivated men applaud novels and plays in proportion to the fidelity with which they exhibit characters. improbabilities, like the impossibilities which preceded them, are disallowed; and we see fewer of those elaborate plots which life rarely furnishes: realities are more definitely pictured.

§138. Space might be filled with evidences of other kinds, but the basis of induction is already wide enough. Proof that all Evolution is from the indefinite to the definite, we find not less abundant than proof that all Evolution is from the homogeneous to the heterogeneous.

It should, however, be added that this advance in definiteness is not a primary but a secondary phenomenon — is a result incidental on other changes. The transformation of a whole that was originally diffused and uniform into a concentrated combination of multiform parts, implies progressive separation both of the whole from its environment and of the parts from one another. While this is going on there must be indistinctness. Only as the whole gains density, does it become sharply marked off from the space or matter lying outside of it; and only as each division draws into its mass those peripheral portions which are at first imperfectly disunited from the peripheral portions of neighbouring divisions, can it acquire anything like a precise outline. That is to say, the increasing definiteness is a concomitant of the increasing consolidation, general and local. While the secondary re-distributions are ever adding to the heterogeneity, the primary redistribution, while augmenting the integration, is incidentally giving distinctness to the increasingly unlike parts as well as to the aggregate of them.

But though this universal trait of Evolution is a necessary accompaniment of the traits set forth in preceding chapters, it is not expressed in the words used to describe them. It is therefore needful further to modify our formula. The more specific idea of Evolution now reached is — a change from an indefinite, incoherent homogeneity, to a definite coherent heterogeneity, accompanying the dissipation of motion and integration of matter.